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Hi All,

I'm trying my hand at fixing an old 240 that has been around town for several years and has NEVER run decently. It pings like crazy with the timing set at anything even close to 10 degrees. I have to back it off to 2 or 3 degrees, or even 0 on a warm day. Then it runs badly.

It has surprisingly high compression (155-165 psi dry) and while looking for what's going on, I discovered that it has an L26 block. I have no idea what sort of pistons are in it -- but I sort of expect stock '74 pistons -- whatever they are. It has an E88 head that I don't think has been cut much if any, 'cause the cam timing is good.

Anyone have any idea what sort of compression ratio this combination gives?

Should I just stick one of my spare L24 bottom ends in?

Any advice appreciated, thanks

Pat
 

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About 9.2:1, well within limits for pump gas

Here's how to calculate the c.r.

Cylinder Volume:
Bore(cm) x Stroke\2(cm) x pi/4
7.9 x 8.3\2 x .7853982 =427.4cc

Chamber volume:
Head Volume + Gasket Volume + Piston Dish cc or - Piston Dome cc

44.7cc (Stock E88 combustion chamber volume)+ 7.6cc (stock gasket volume) = 53.3cc

Compression Ratio:
cylinder vol. + chamb. vol. / chamb. vol.
427.4 + 53.3 / 53.3 = 9.17~9.2:1

It sounds as if the engine is in good shape, as far as compression. Sounds like a timing or ignition problem to me.
 
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